Studies will be carried out to determine the relationship of high lithium concentrations in drinking water, with and without fluoride, on caries prevalence in a population of school children in Texas, U.S.A. An epidemiologic survey of dental caries prevalence will be carried out on 12-14 year old school children living in 6 towns/cities in Texas. These communities will reflect high and low lithium (0.0 to 100 Mug/1) in combination and low fluoride (0.1 to 1.8 mg/1) in their drinking water supplies. The trace element concentrations willbe related to dental caries prevalence. Diagnosis of dental caries will be by established methods using the visual-tactile techniques. Caries will be recorded as DMFT and OMFS for life-long resident children and immigrants. Oral hygiene scores will be recorded using a partial recording system and mottling, opacities and pigmentation by a standardized diagnotic procedure. On a sub-set of 14 year old males, plaque will be collected on the day following the dental examinations. A minimum o 25 subjects from each community will be chosen to represent high and low caries individuals. Plaque samples will be analyzed for lithium, fluoride, calcium and phosphorous on a dry weight basis. Concentrations of lithium and fluoride will be related to individual and group caries prevalence scores.